1. Field of Invention
This invention relates to sampling devices and, more particularly, to devices which receive samples from a flowing fluid line, such as a process line.
2. Description of Prior Art
In many processes, such as those involved in manufacturing and industrial operations, it is imperative that samples be taken from lines of flowing fluid. It is desirable that such samples be taken so as to avoid contamination of the sample, as well as to avoid contamination of the surrounding environment. Since a minimal disturbance of the process flow is also desirable, the sample is usually taken under pressure by tapping a conduit containing the flowing medium to be sampled. This is accomplished by tapping the process line with a sample line and providing a valve which can be opened to allow a sample of the fluid to escape into a sample receptacle. Because of the hazardous nature of many process fluids, it is desirable that human contact with the sample be minimized.
Examples of patented sampling devices may be seen by examining the following patents, which are incorporated herein by reference:
U.S. Pat. No. 2,844,964 (Guibert) PA1 U.S. Pat. No. 2,693,705 (Casler) PA1 U.S. Pat. No. 3,276,265 (Taft) PA1 U.S. Pat. No. 3,383,923 (Conche, et al) PA1 U.S. Pat. No. 3,872,730 (Ringrose) PA1 U.S. Pat. No. 4,014,216 (Thorton, et al) PA1 U.S. Pat. No. 4,118,987 (Zeh) PA1 U.S. Pat. No. 4,174,632 (Jansen) PA1 U.S. Pat. No. 4,380,176 (Bauer, et al) PA1 U.S.S.R. patent No. 549,706
From an examination of the above listed patents, it will become apparent that it is generally known to provide a sampling mechanism whereby sample fluid from a valve passes through a hollow needle, which is inserted through a septum in a removable sample container, thus filling the container. Because a substantial seal is created between the septum and the needle, a vent must be provided in the sample container in order for fluid under pressure to safely enter the container. In Jansen and Zeh, listed above, the vent is provided by a second needle.
The two needle approach described above has proven to be unsatisfactory. By puncturing the septum twice, there is a greater possibility of leakage should the sample container be over-filled. Substances, such as hazardous acids, etc., would then contaminate and possibily damage process equipment, pollute the environment and possibly injure the personnel involved in collecting the sample. Also, the needles disclosed in the prior art are beveled so as to produce a sharp edge which cuts as it penetrates a septum. This cutting action results in a poor seal between the needle and the septum, further resulting in an increased probability of leakage.
Also, the presence of two needles has created the problem of multiple punctures in the septum as a sample container is repeatedly removed and then re-installed. Looking at the Zeh patent, for example, if the sample container were rotated slightly and then re-installed, the needles would pierce the septum at different points, resulting in leakage through the original puncture holes in the septum. The Jansen device attempted to solve this problem by providing side-by-side needles which are centered so as to pierce the septum in the same place, regardless of the rotational position of the sample container. This arrrangement has also proven unsatisfactory, in that an inadequate seal is formed when the two needles are reinserted into the same puncture hole.